Some radiation imaging apparatus performs radiation imaging by a photon counting scheme of detecting each radio-photon and counting the number of photons. More specifically, the radiation imaging apparatus includes, for example, a pixel array having an array of a plurality of pixels and a processor. When a radio-photon enters the pixel array, each of pixels corresponding to the entering position of the radio-photon and positions near it in the pixel array outputs a signal corresponding to the amount of energy of the radio-photon.
The processor obtains a plurality of pixel data by reading out signals from a plurality of pixels as one (one-frame) pixel data in a predetermined cycle, and generates radiation image data by using the plurality of pixel data. More specifically, the processor calculates the entering position of a radio-photon and its energy amount based on a signal forming each of a plurality of pixel data, and generates radiation image data based on the calculation result.
As one of the above calculation methods, there may be available a method of specifying the detection areas of radio-photons in a pixel array based on image data and calculating the entering positions and energy amounts of the radio-photons based on the respective pixel signals in the detection areas.